I've written an android application that controls Banshee media player in Linux via your android powered device. The application can be found (for free) in the market under the name Banshee Remote. In order to use it, you need to download this Banshee plugin written by myself and Kristopher Dick. Download the file to /usr/lib/banshee-1/Extensions if you're using Banshee version less than 2.0 or at /usr/lib/banshee/Extensions if you're using Banshee version 2.0 or higher (requires root access).
Once the plugin is downloaded, open up Banshee and go to Edit->Preferences, Extensions tab. Scroll down until you see an entry called "Remote Listener" as shown below:
Check the checkbox next to it and click close. Open the same window (Edit->Preferences) again and you'll notice that another tab has been created labeled "Remote Control":
This controls the port to which the Android device will be bound to. If you don't know what this is you should leave it at the default value 8484. Make sure the port you choose is open and not blocked by any firewalls. Click close and you're done! The Banshee Remote plugin will be now enabled until you disable it in the Extensions tab.
Run the BansheeRemote application on the Android device while connected to the internet, specify the IP address of your computer and the port that you selected in the previous step and you can remotely control Banshee on your computer.
The application is based on Jeffrey Sharkey's Amarok Remote. I found that Sharkey's Amarok Remote was very shaky mostly due to the HTTP connections it relied on, so I rewrote it to use TCP socket connections.
A couple of screenshots:
As of version 4.0 of BansheeRemote, you can now browse the media library of banshee and choose songs to play. After you connect to Banshee via the app, click 'Menu' and press the option 'Sync'. This will copy your Banshee database file on your sd card (so make sure you have one!) and will use it to browse the songs in Banshee. You only need to do this once or whenever you have updated your Banshee Collection. If for some reason this fails, you can manually copy the Banshee database file (usually located in ~/.config/banshee-1/banshee.db) on the root directory of your sd card. Three image buttons on the BansheeRemote UI should allow you to browse artists/albums/songs and the phone's volume buttons should control the volume of Banshee (if BansheeRemote is open). Another thing to keep in mind is that you have enough space on your sd-card to hold the banshee.db file. For my collection which has ~45GB of music, the file is ~8MB.
Here is a tarball of the source code for BansheeRemote and here is the .apk for manual installation. Here is the source code for the Banshee plugin. I am sure the code can be improved so any improvements are welcome. Everything here is released under GPLv3.